JPH05323160A - Glass fiber for optical transmission - Google Patents

Abstract

(57) [Summary] [Structure] In a glass fiber for optical transmission in which a coating layer of an ultraviolet curable resin is provided on the outer circumference of the glass fiber for optical transmission, the Young's modulus of the resin used for the outermost layer is 100 k
A glass fiber for optical transmission having a g / mm ² or more and an elongation of 30% or more. The coating diameter of the outermost layer is 200 μm or less. [Effect] It is possible to provide a thin coated optical fiber capable of maintaining lateral pressure resistance characteristics, optical transmission characteristics, and fiber strength that are equal to or higher than those of conventional coated optical fibers, and is extremely effective in increasing the density of optical cables.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass fiber for optical transmission used for optical communication, which has particularly excellent lateral pressure characteristics and optical transmission characteristics, and more particularly a glass fiber for thin-walled optical transmission (coating diameter). : 200 μm or less)
It is about. In particular, the present invention relates to improvement of coating resin in resin-coated optical fibers.

[0002]

2. Description of the Related Art A glass fiber for optical transmission (optical glass fiber) has a problem in maintaining mechanical characteristics and optical transmission characteristics in the as-drawn state. And the like.

As the material, an ultraviolet curable resin (hereinafter referred to as UV resin) is generally used from the viewpoint of productivity. The coating generally has a two-layer structure, and a relatively soft buffer layer (coating diameter: about 200 μmφ, as an inner layer,
Young's modulus: about 0.1 to 0.2 kg / mm ² ) is provided, and a hard protective layer (coating diameter: about 250 μm) is provided on the outer periphery thereof.
φ, Young's modulus: 30 to 100 kg / mm ² ). By the way, in recent years, in order to promote the opticalization of telephone networks, it is necessary to further increase the density of cables.

In a tape slot type cable in which a plurality of UV resin-coated optical fibers are bundled in parallel and tape-shaped optical glass fibers joined by a common UV resin coating are assembled, a conventional fiber has a coating outer diameter (about 250 μmφ). As it is, there is no limit to increasing the density, and thinning of the coating (coating diameter of the outermost layer of 200 μmφ or less) is being promoted. However, in a thin-wall coated optical fiber (a coating outer diameter of 200 μmφ or less) using a conventional UV resin (Young's modulus: 30 to 100 kg / mm ² ) as a coating material for the outermost layer, the lateral pressure resistance is high due to the thinness of the coating layer. Extreme deterioration of characteristics has occurred.

Therefore, a thin coated optical fiber (coated outer diameter 2
In the case of 00 μmφ or less), the UV resin used for the outermost layer has an ultra-high Young's modulus in order to improve lateral pressure characteristics. As a result, the lateral pressure resistance characteristic equivalent to that of the conventional coated optical fiber (coated outer diameter of about 250 μmφ) is maintained. It should be noted that the lateral pressure characteristic referred to here is a series of characteristics in which a slight bending occurs in the fiber when the outside (lateral pressure) is applied to the fiber, and as a result, the optical transmission loss increases.

[0006]

However, a thin-walled optical fiber whose outermost layer is coated with a UV resin having an ultra-high Young's modulus (100 kg / mm ² or more) (outer diameter of 200 μm)
In the following), the optical transmission characteristics are deteriorated and the screening rupture strength is reduced.

This is because the UV resin used for the outermost layer has a high Young's modulus and an extremely small elongation property (about 6%), so that the scratches on the coating surface are apt to be cracks due to bending stress, and the outermost layer coating is unsatisfactory. It causes bending and gives non-uniform distortion to the glass part, deteriorating the optical transmission characteristics. Further, the growth of the cracks easily breaks during screening. It is believed that.

Here, the screening is a test for guaranteeing the minimum strength in the longitudinal direction by applying a constant tension to the entire length of the fiber. Elongation is the percentage of the ratio of the elongation between the gauge points of the test piece to the original gauge point distance before the test piece breaks in the tensile test.

[0009]

As a result of various studies to solve the above problems, the inventors of the present invention have found that in a thin-wall coated fiber (coated outer diameter of 200 μmφ or less), the Young's modulus of the coating resin of the outermost layer is 100 kg. / Mm ² or more and an elongation of 30% or more, it has been found that while maintaining excellent lateral pressure characteristics, good optical transmission characteristics can be maintained and screening strength can be improved. We were able to reach the glass fiber for optical transmission.

That is, according to the present invention: In an optical transmission glass fiber in which at least one coating layer made of an ultraviolet curing resin is provided on the outer circumference of the optical transmission glass fiber, the ultraviolet curing resin used as the outermost layer is used. A glass fiber for optical transmission, having a Young's modulus of 100 kg / mm ² or more and an elongation of 30% or more, and the outermost layer of the glass fiber for optical transmission has a coating diameter of 200.
The glass fiber for optical transmission for thin coating having a thickness of μm or less is characterized.

The present invention will be described in detail below with reference to the drawings. The glass fiber for optical transmission of the present invention is basically shown in FIG.
The multi-layer structure as shown in, preferably at least a two-layer structure from the viewpoint of thinning. That is, the outermost layer of the glass optical fiber 1 is provided with the protective layer 3 having a specific physical property value of the present invention via the buffer layer 2.

The ultraviolet curable resin forming the outermost protective coating 3 is an ultraviolet curable resin, and is not particularly limited as long as it has the functions of high Young's modulus and high elongation. Epoxy acrylates, urethane acrylates, ester acrylates and the like are preferable because the effects of increasing the Young's modulus and increasing the elongation can be relatively easily obtained. These may be used alone (generally in the form of an oligomer), but may also be used in combination with a photoinitiator or a polyfunctional monomer.

As the buffer layer 2, the ultraviolet curable resin of the outermost layer may be appropriately used, or a relatively soft coating material such as silicone resin may be used. Of course, if necessary, a layer that is the same as or different from the material for the protective layer or the buffer layer may be further provided. The optical transmission glass fiber of the present invention can be easily manufactured by a conventional optical fiber manufacturing apparatus as shown in FIG.

[0014]

The outermost coating 3 serves as a shell for protecting the glass from external pressure. Therefore, the higher the Young's modulus of the coating 3, the stronger the external pressure (side pressure). However, on the other hand, when the elongation property is small, it is extremely brittle and easily cracked when bent.

It is considered that this causes inhomogeneity of the coating surface, strains the glass to deteriorate the optical transmission characteristics, and eventually reduces the fiber strength. Therefore, it is necessary to increase the elongation characteristics as the Young's modulus of the outermost layer coating resin is increased. In the present invention, as a result of various examinations and investigations on the relationship between the Young's modulus and elongation of the outermost layer coating material and the optical transmission characteristics, particularly, thin-walled coated fiber (coated outer diameter 200 μm
The range of Young's modulus and elongation characteristics that improve the optical transmission characteristics was found while maintaining the lateral pressure resistance characteristics at mφ or less).

By the way, the conventional fiber (coating diameter: 25
(About 0 μmφ), the coating layer is sufficiently thick,
The effect of increasing the Young's modulus of the outermost layer coating was small, and the necessity thereof was not so large. However, in the case of a thin coating fiber with a thin coating layer (coating outer diameter; 200 μmφ or less),
The effect of increasing Young's modulus and increasing elongation as in the present invention is indispensable.

[0017]

The present invention is illustrated by the examples, which do not limit the scope of the invention. Using the optical fiber manufacturing apparatus shown in FIG. 4, the optical fiber preform 4 is drawn in the drawing furnace 5 to obtain the glass optical fiber 1. After the resin coating is provided on the optical fiber 1 by passing the optical fiber 1 through the resin coating device 6, the ultraviolet ray curable resin coating is cured by the ultraviolet ray irradiation device 9 provided with the ultraviolet ray irradiation lamp 7. A thin optical fiber 1 having the structure shown was obtained.

For the inner layer (buffer layer) 2, a UV-curable urethane acrylate resin having a Young's modulus of 0.10 kg / mm ² at room temperature was commonly used, and the coating outer diameter was 150 μmφ. On the other hand, for the outer layer (protective layer) 3, various UV-curable urethane acrylate resins having different Young's moduli and elongation characteristics as shown in Table 1 were used to finish the coating outer diameter to 180 μmφ.

The lateral pressure characteristics and optical transmission characteristics of each coated optical fiber were investigated. The results are shown in Table 1. The characteristics of the conventional coated optical fiber (coating outer diameter 250 μm) are also shown.

[0020]

[Table 1]

Note) * 1) Flat plate side pressure test: increase in transmission loss at a load of 50 kg; expressed by Δα (1.55 μm). * 2) Optical transmission characteristics (1.55μ in the bobbin winding state)
m). * 3) Number of breaks per 100 km in 700 g screening test. * 4) Young's modulus and elongation are measured according to JIS method .

Further, FIG. 1 shows the relationship between the Young's modulus of the outermost layer coating resin of the coated optical fibers A to F shown in Table 1 and the lateral pressure characteristic. FIG. 2 shows the relationship between elongation characteristics and optical transmission characteristics.

From these results, it is understood that by setting the Young's modulus of the coating resin used for the outermost layer to 100 kg / mm ² or more, the lateral pressure characteristic equivalent to that of the conventional fiber can be obtained. Further, it was found that by setting the elongation property to 30% or more, it is possible to obtain a thin-coated optical fiber having the same optical transmission property and fiber strength as the conventional fiber.

In the above description, the case where each of the inner layer and the outer layer is one layer has been described as an example. However, in the coated optical fiber having the ultraviolet curable resin coating of at least one layer on the outer circumference of the fiber, the present invention is the outermost layer. If the Young's modulus and elongation characteristics of are within the limits of the present invention, similar effects can be obtained.

[0025]

As described above, according to the present invention, the lateral pressure resistance characteristic, the optical transmission characteristic, which is equal to or higher than that of the conventional coated optical fiber,
It is possible to provide a thin-coated optical fiber (having a coating outer diameter of 200 μmφ or less) that can maintain the fiber strength, which is very effective for increasing the density of the optical cable.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between Young's modulus and lateral pressure characteristics of the outermost layer coating resin used in the present invention.

FIG. 2 is a graph showing the relationship between the elongation characteristics and the light transmission characteristics of the outermost layer coating resin used in the present invention.

FIG. 3 is a cross-sectional view of an example of a resin-coated optical fiber of the present invention.

FIG. 4 is a schematic diagram showing an outline of an optical fiber manufacturing apparatus used for manufacturing the optical transmission fiber of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass optical fiber 2 Buffer layer 3 Protective layer (outermost layer) 4 Optical fiber base material 5 Drawing furnace 6 Resin coating device 7 Ultraviolet irradiation lamp 8 Cylindrical body 9 Ultraviolet irradiation device 10 Reflecting mirror 11 Resin coating optical fiber 12 Winding Machine

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Juya Tsunoda 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Wataru Katsurajima 1-tani, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Denki Kogyo Co., Ltd. Yokohama Works (72) Inventor Hiroo Matsuda 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Denki Kogyo Co., Ltd. Yokohama Works (72) Inventor Shigeru Tomita 1-1-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 6 Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A glass fiber for optical transmission comprising at least one coating layer made of an ultraviolet curable resin on the outer circumference of the glass fiber for optical transmission, wherein the Young's modulus of the ultraviolet curable resin used for the outermost layer is 100 kg. / Mm ² or more, elongation is 30% or more, a glass fiber for optical transmission. 2. The coating diameter of the outermost layer of the optical transmission glass fiber is 200 μm or less.
The glass fiber for optical transmission according to.